Combined two engine cycle with at least one recuperated cycle engine for rotor drive

ABSTRACT

A drive architecture comprises a rotor and a gearbox for driving the rotor. A pair of input gears provides rotational drive to the gearbox. A first recuperative cycle engine drives one of the pair of gears and a second engine drives the other of the pair of gears. The first recuperative cycle engine and the second engine are both gas turbine engines. A power takeoff from a drive shaft of the second engine supplies rotational drive to drive at least one component in the first recuperative cycle drive.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/019,478, filed Jul. 1, 2014.

BACKGROUND OF THE INVENTION

This application relates to a combination of two distinct engine typeswhich can be efficiently utilized to drive a rotor.

Gas turbine engines are known and are used to drive a variety ofaircraft. One known type of gas turbine engine is a so-calledrecuperated cycle engine. In such an engine, heat is captured and usedto heat air downstream of a compressor prior to being delivered into acombustion section.

Another type of gas turbine engine is a simple cycle engine wherein suchpreheating does not occur.

Each type engine has its strengths.

Gas turbine engines have been utilized to drive rotary wing aircraft,such as a propeller system for a helicopter. Typically, a pair ofengines are placed on the helicopter. Under certain conditions, drivefrom both of the engines is required. However, under many standardoperating conditions, only one of the engines is sufficient to provideadequate power.

Pilots for such a rotary wing aircraft will often drive both engines asa safety measure.

SUMMARY OF THE INVENTION

In a featured embodiment, a drive architecture comprises a rotor and agearbox for driving the rotor. A pair of input gears provides rotationaldrive to the gearbox. A first recuperative cycle engine drives one ofthe pair of gears and a second engine drives the other of the pair ofgears. The first recuperative cycle engine and the second engine areboth gas turbine engines. A power takeoff from a drive shaft of thesecond engine supplies rotational drive to drive at least one componentin the first recuperative cycle drive.

In another embodiment according to the previous embodiment, the powertakeoff from the second engine serves to provide rotational input todrive a compressor in the first recuperative cycle engine.

In another embodiment according to any of the previous embodiments, airdownstream of the compressor in the first recuperative cycle engine isdirected through a heat exchanger downstream of a turbine section in thefirst recuperative cycle engine. The air is heated and is then returnedinto a combustor section, which is intermediate the compressor and theturbine section in the first recuperative cycle engine.

In another embodiment according to any of the previous embodiments, airis tapped from the second engine downstream of a compressor in thesecond engine and passed into a second heat exchanger where itadditionally provides heat to the air from the compressor in the firstrecuperative cycle engine before the air in the first recuperative cycleengine is returned to the combustion section.

In another embodiment according to any of the previous embodiments, theair from the second engine is passed from a location downstream of asingle compressor rotor and through the second heat exchanger.

In another embodiment according to any of the previous embodiments,there are at least two compressor rotors in the compressor of the secondengine. Air is passed into the second heat exchanger from the secondengine at a location intermediate a first and second compressor rotor inthe second engine.

In another embodiment according to any of the previous embodiments, abypass feature is provided on the tap from the second engine into thesecond heat exchanger with the bypass being provided with valving toselectively deliver air from the second engine to the second heatexchanger or bypass air back to the second engine.

In another embodiment according to any of the previous embodiments, thedrive shaft for the recuperative cycle engine also rotates a thrustpropeller.

In another embodiment according to any of the previous embodiments, thesecond engine is a reverse core engine wherein air is delivered along apath past a turbine section in the second engine, past a compressor inthe second engine, and then turned into the compressor for the secondengine.

In another embodiment according to any of the previous embodiments, airdownstream of the turbine section in the first recuperative cycle enginepasses through a thrust nozzle.

In another embodiment according to any of the previous embodiments, thethrust nozzle is a variable area nozzle.

In another embodiment according to any of the previous embodiments, thepower takeoff drives a generator to generate electricity.

In another embodiment according to any of the previous embodiments, thegenerator provides power to a power electronic system which, in turn,drives the mechanical connection.

In another embodiment according to any of the previous embodiments, amechanical connection and a generator communicate with the powerconnection and with a shaft for the compressor in the second engine.

In another embodiment according to any of the previous embodiments, themechanical connection provides power to the shaft for the compressor andthe second engine.

In another embodiment according to any of the previous embodiments, themechanical connection receives the rotary drive from the shaft of thecompressor of the second engine.

In another embodiment according to any of the previous embodiments, thepower takeoff drives a generator to generate electricity.

In another embodiment according to any of the previous embodiments, thegenerator provides power to a power electronic system which, in turn,drives the mechanical connection.

In another embodiment according to any of the previous embodiments, amechanical connection and a generator communicate with the powerconnection and with a shaft for the compressor in the second engine.

In another embodiment according to any of the previous embodiments, themechanical connection provides power to the shaft for the compressor andthe second engine.

In another embodiment according to any of the previous embodiments, themechanical connection receives the rotary drive from the shaft of thecompressor of the second engine.

These and other features may be best understood from the followingdrawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first schematic drive system for a rotary wing aircraft.

FIG. 2A shows a second embodiment.

FIG. 2B shows an alternative.

FIG. 3 shows a third embodiment.

FIG. 4 shows a feature that may be incorporated into theabove-referenced embodiments.

FIG. 5 shows another feature that may be incorporated into theembodiments.

FIG. 6 shows an alternative embodiment.

FIG. 7A shows yet another alternative.

FIG. 7B shows yet another alternative.

DETAILED DESCRIPTION

A rotary wing aircraft drive 20, such as a propeller system for ahelicopter, is illustrated in FIG. 1. A main rotor gearbox 22 drives thepropeller system 20. A pair of input drive gears 26 and 30 are shownschematically driving the gearbox 22. Gear 26 is driven by a shaft 24 onan engine 18. Gear 30 is driven by a shaft 28 which is part of an engine19.

Engine 19 is a “reverse core” engine. Thus, an inlet duct 52 deliversair to a turning end 56, where it is then delivered into a compressor54. The air is compressed in compressor 54, delivered into a combustionsection 58, mixed with fuel and ignited. Products of this combustionpass downstream over a turbine rotor 60, which drives the compressorrotor 54. Downstream of the turbine rotor 60, the products of combustiondrive another turbine rotor 34 which drives the shaft 28. Downstream ofthe turbine rotor 34, the products of combustion are reversed through anexit duct 35.

The engine 18 has an inlet duct 17 delivering air into a compressor 32.Compressor 32 delivers air into a combustion section 42, where it ismixed with fuel and ignited. Products of this combustion drive a turbinerotor 44, which, in turn, drives a shaft 46 to drive the compressorrotor 32.

Downstream of the turbine rotor 44, the products of combustion driveanother turbine rotor 35 to, in turn, drive the shaft 24 and adownstream shaft portion 36, which drives a thrust propeller 38.

Engine 18 is a recuperative engine, while engine 19 is a simple cycleengine. A simple cycle engine has one instance of heat input withoutwork being added or subtracted. The heat input typically is a combustor.A recuperative, or regenerative cycle recycles a fraction of the heatinput by the combustor by transferring heat from the gas flow ofproducts of combustion exiting the turbine to the air flow that exitsthe compressor and enters the combustor. The heat transfer devicetypically is a heat exchanger.

In a regenerative cycle, the temperature of the air flow exiting thecompressor is lower than the temperature of the gas flow exiting theturbine; hence, heat can be transferred from the gas flow to the airflow. This reduces the heat input required of the combustor.

In a simple cycle, the temperature of the air flow exiting thecompressor is higher than the temperature of the gas flow exiting theturbine; hence, heat cannot be transferred from the gas flow to the airflow of the simple cycle engine. However, heat can be transferred fromthe air flow of the simple cycle engine to the air flow of theregenerative cycle engine. Transferring heat from the air flow of thesimple cycle engine intercools the air flow of the compressor of thesimple cycle engine, lowering the compressor exit temperature of theairflow of the simple cycle. Controlling compressor exit temperature isadvantageous when the ambient air inlet temperature of the compressor ishigh. The combination synergistically controls the inlet temperature ofthe combustor for each engine.

As can be appreciated from the schematic of FIG. 1, air downstream ofthe compressor rotor 32 passes through a heat exchanger 40, where it isheated by the products of combustion downstream of the turbine rotor 35.The air may also pass to a heat exchanger 50 where it is heated by airfrom tap 62, which has been heated in the compressor 54.

Thus, when the air returns from the heat exchanger 50 to the inlet tothe combustor 42, it has been preheated and, thus, the combustion isperformed more efficiently.

In addition, a gear 76 rotates with the compressor 32 and receives drivefrom a bevel gear 74. Bevel gear 74 is driven by a gear 70, driven bythe shaft 28.

When the associated aircraft driven by the propeller system 20 is beingdriven in a condition where it does not need both engines, the engine 19supplements power to engine 18 through the gear 74. The gear and shaftcombination 72/74 drive the gear 76 and supply power to the compressor32. This saves power that the turbine 44 would otherwise have to deliverto the compressor 32 and results in higher temperatures preheating theair in the heat exchanger 40. As such, this cycle operates moreefficiently.

FIGS. 2A and B show an engine system, wherein features generallyidentical to those of FIG. 1 are simply identified by a number moved 100higher.

A difference is that the engine 119 now has two compressor rotors 180and 182 and an intercooler 184 is passed through the heat exchanger 150,rather than the air downstream of the entire compressor section beingdelivered into the combustion section. Otherwise, this combinationoperates in a manner similar to that of FIG. 1.

In contrast, in FIG. 2B, a portion 15 of the refrigerant downstream ofthe compressor stage 182 is tapped as the intercooler 184, and isreturned at 13 downstream of the compressor stage 180. A portion of theair compressed at stage 182 does pass the stage 180, and is then mixedwith the returning fluid 13.

FIG. 3 shows an engine wherein features identical to FIGS. 2A/B areidentified by the number 200 added to the reference arrows in FIGS.2A/B.

Here, the thrust propeller has been replaced by a thrusting nozzle 289,which may be a variable nozzle, as is otherwise known.

FIG. 4 shows the heat exchanger 350 and a feature which may be placed onthe line 313 leading from the compressor section through the heatexchanger 350. As shown, a shutoff valve 385 may be controlled incombination with the valve 386 to divert air through a line 387, when itis not desired to achieve the intercooling.

An appropriate control 391 controls the valves 385 and 386 and a workerof ordinary skill in the art would understand when to provide suchcontrol.

FIG. 5 shows an embodiment wherein the connection between the engine isutilized to generate electrical power. As is shown, the gear 374 drivesa shaft 372 which, in turn, drives a generator 375. Generator 375 powersa power electronics 377 which can provide electrical power to a use 376.The power electronics 377 drives a combined motor and mechanicalconnection 379 that passes rotational power to a shaft 380, such that itcan supply drive to the recuperative engine, as in the priorembodiments.

FIG. 6 shows an embodiment, wherein the input gears 600 drives a shaft602 to, in turn, drive a generator 679. Generator 679 supplies power tothe power electronics 677. Motor and mechanical connection 680 receivespower from the power electronics 677 to drive shaft 602. The combinationof 680/679 also is known in the art as a motor/generator.

Downstream of the power electronics, another generator 681 generateselectricity and supplies it back to the power electronics 677 and alsodrives a combined motor and mechanical connection 682, which drives theshaft portion 683 to supply mechanical energy to the recuperative engine618. Another generator 681 generates electricity and supplies it back tothe power electronics 677 and also drives the motor 682, which drivesthe shaft portion 683 to supply mechanical energy to the recuperativeengine 618. Here again, a use 676 for generated electrical power isdisclosed schematically. Mechanical power from engine 618 is convertedto electrical power that is converted back to mechanical power to drivegear 600 that drives gear 670 and shaft 628 of engine 619. Thecombination of 682/681 also is known in the art as a motor/generator.

FIG. 7A shows an embodiment which may be incorporated into theembodiments of FIG. 5 or 6. A generator 706 receives power from the line700 which may be the power electronics in the FIG. 5 or 6 embodiment. Itdrives the mechanical connection 708 to supply power to a shaft 702,which drives a compressor 704.

FIG. 7B shows another embodiment wherein the compressors 808 and 810rotate with a shaft 806 to, in turn, drive a mechanical connection 804to generate electricity at generator 802 and supply that generatorelectricity though a line 800 back to the power electronics as in theFIG. 5 or 6 embodiments.

While a propeller system for a rotary wing aircraft is specificallydisclosed, other gearbox applications for driving a rotor may benefitfrom these teachings. As an example, certain aircraft are provided witha lift fan, and a rotor for such a fan may well benefit from the drivearchitecture of this disclosure.

Although a number of embodiment of this invention has been disclosed, aworker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

The invention claimed is:
 1. A drive architecture comprising: a rotorand a gearbox for driving said rotor; a pair of input gears forproviding rotational drive to said gearbox and a first recuperativecycle engine driving one of said pair of gears and a second enginedriving the other of said pair of gears; said first recuperative cycleengine and said second engine both being gas turbine engines, with apower takeoff from a drive shaft of said second engine supplyingrotational drive to drive at least one component in said firstrecuperative cycle drive; and wherein air downstream of a compressor insaid first recuperative cycle engine is directed through a heatexchanger downstream of a turbine section in said first recuperativecycle engine, the air is heated by products of combustion downstream ofsaid turbine section in said first recuperative cycle engine and is thenreturned into a combustor section in said first recuperated cycleengine, which is intermediate said compressor and said turbine sectionin said first recuperative cycle engine.
 2. The drive architecture asset for in claim 1, wherein said power takeoff from said second engineserves to provide rotational input to drive a compressor in said firstrecuperative cycle engine.
 3. The drive architecture as set for in claim1, wherein air is tapped from said second engine downstream of acompressor in said second engine and passed into a second heat exchangerwhere it additionally provides heat to the air from said compressor insaid first recuperative cycle engine before the air in said firstrecuperative cycle engine is returned to said combustion section.
 4. Thedrive architecture as set for in claim 3, wherein said air from saidsecond engine is passed from a location downstream of a singlecompressor rotor and through said second heat exchanger.
 5. The drivearchitecture as set for in claim 3, wherein there are at least twocompressor rotors in the compressor of said second engine and the air ispassed into said second heat exchanger from said second engine at alocation intermediate a first and second compressor rotor in the secondengine.
 6. The drive architecture as set for in claim 3, wherein abypass feature is provided on said tap from said second engine into saidsecond heat exchanger with said bypass being provided with valving toselectively deliver air from said second engine to said second heatexchanger or bypass air back to said second engine.
 7. The drivearchitecture as set for in claim 1, wherein said drive shaft for saidrecuperative cycle engine also rotates a thrust propeller.
 8. The drivearchitecture as set for in claim 1, wherein said second engine is areverse core engine wherein air is delivered along a path past a turbinesection in said second engine, past a compressor in said second engine,and then into the compressor for said second engine.
 9. The drivearchitecture as set for in claim 1, wherein air downstream of theturbine section in the first recuperative cycle engine passing through athrust nozzle.
 10. The drive architecture as set for in claim 9, whereinsaid thrust nozzle is a variable area nozzle.
 11. The drive architectureas set for in claim 1, wherein said power takeoff driving a generator togenerate electricity.
 12. The drive architecture as set for in claim 11,wherein said generator providing power to a power electronic systemwhich, in turn, drives a mechanical connection.
 13. The drivearchitecture as set for in claim 1, wherein a mechanical connection anda generator communicate with said power connection and with a shaft forsaid compressor in said second engine.
 14. The drive architecture as setfor in claim 13, wherein said mechanical connection providing power tosaid shaft for said compressor of said second engine.
 15. The drivearchitecture as set for in claim 13, wherein said mechanical connectionreceiving a rotary drive from said shaft of said compressor of saidsecond engine.
 16. The drive architecture as set for in claim 1, whereinsaid power takeoff driving a generator to generate electricity.
 17. Thedrive architecture as set for in claim 16, wherein said generatorproviding power to a power electronic system which, in turn, drives amechanical connection.
 18. The drive architecture as set for in claim16, wherein a mechanical connection and a generator communicate withsaid power connection and with a shaft for a compressor in said secondengine.
 19. The drive architecture as set for in claim 18, wherein saidmechanical connection providing power to said shaft for said compressorof said second engine.
 20. The drive architecture as set for in claim18, wherein said mechanical connection receiving said rotary drive fromsaid shaft of said compressor of said second engine.